8. Anencephaly

10. Spina bifida occulta with meningocoele

11. Spina bifida with failure of neuropore closure

12. Cortical dysplasia

14. Support cells (neuroglia) - more abundant than neurons - more mitotic capability

15. Astrocytes 1. Fill-in the space between neurons and blood vessels in brain. 2. Most numerous glial cells in brain. 3. Form the blood-brain barrier

16. Astrocytes 4. Envelope synapses, preventing spread of neurotransmitter. 5. Take up and store neurotransmitter from the extracellular environment (ECF). 6. Their membranes possess neurotransmitter receptors. Electrical and biochemical events can be triggered in these cell.

17. Astrocytes 7. Can even release some of the stored neurotransmitters. May have an adjunct role. 8. Can “sherpa” the growth of new neurons or processes.

18. Potassium spatial buffering

19. Astrocytoma

20. Oligodendrocytes

21. Demyelination (with plaques) Characteristic of MS

22. Oligodendroglioma

24. Ependymal cells

26. Microglia

27. Schwann cells

28. Schwann cells can regenerate damaged axons

29. Neurofibromatosis caused by loss of tumor suppressor gene neurofibromin

30. Neurofibromatosis

31. Gated Ion Channels A. Gated Na + channels 1. localization a. voltage-gated

32. - large concentration in hillock - found along the axon

33. Gated Ion Channels A. Gated Na + channels 1. localization b. ligand-gated at synapses

34. Gated Ion Channels A. Gated Na + channels 1. localization Na + channels occupy only a small fraction of surface area 100-500 channels/  m

35. Gated Ion Channels 2. Often have two gates a. activation (fast) b. inactivation (slow)

36. Gated Ion Channels 3. factors contributing to specificity a. anions at mouth of channel b. size c. ability to dehydrate (shed water of hydration)

37. Electrical Properties of Membranes A. Conductance (g) 1. conferred by ion channels 2. is inversely related to resistance

38. Electrical Properties of Membranes B. Current - net flow of ions through the channel

39. Electrical Properties of Membranes C. Capacitance 1. conferred by membrane itself bilayer is an insulating layer separating charges

40. 2. capacitative current - ability of ions to interact across the membrane without crossing the bilayer

41. - charges collect on either side of the membrane - energy of the charges “stored” by the capacitor

42. Gated Na + Channels A. Voltage-gated Na + channels 1. current flow a. Na + ions flow through channel at 6000/sec at emf of -100mV b. number of open channels depends on time and V m

43. Gated Na + Channels A. Voltage-gated Na + channels 2. opening of channel a. gating molecule responding to voltage change

44. The number and type of ion channels determines the electrical responses and characteristics of the cell.